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Unable to resolve java build / Spring

First Thing to say, I am a relatively inexperienced programmer.
My task is to import a given gradle project into Spring Boot Tool Suite (sts). I have already download springboot cli, java, gradle. & In the past, I was able to run spring perfectly on another project, unfortunately I had to get my hard drive replaced, so I lost a considerable amount of downloads.
Nonetheless, my issue is two-parted. Firstly, my tool suite (ide? It's basically eclipse) does not recognize my project as a a java project, I have tried many options & the only was to fix that portion is to hardcode org.eclipse.core.javabuilder within the buildCommand tag in my .project file, which I don't remember doing for my last project.
Here is the directory tree of the backend folder(don't concern with the frontend)
.
├── build.gradle
├── gradle
│   └── wrapper
│   ├── gradle-wrapper.jar
│   └── gradle-wrapper.properties
├── gradlew
├── gradlew.bat
├── settings.gradle
└── src
├── main
│   ├── java
│   │   └── ca
│   │   └── mcgill
│   │   └── ecse321
│   │   └── eventregistration
│   │   ├── EventRegistrationApplication.java
│   │   ├── controller
│   │   │   ├── ApiError.java
│   │   │   ├── EventRegistrationRestController.java
│   │   │   └── RestExceptionHandler.java
│   │   ├── dao
│   │   │   ├── EventRegistrationRepository.java
│   │   │   ├── EventRepository.java
│   │   │   ├── PersonRepository.java
│   │   │   └── RegistrationRepository.java
│   │   ├── dto
│   │   │   ├── EventDto.java
│   │   │   ├── PersonDto.java
│   │   │   └── RegistrationDto.java
│   │   ├── model
│   │   │   ├── Event.java
│   │   │   ├── Person.java
│   │   │   ├── Registration.java
│   │   │   └── RegistrationManager.java
│   │   └── service
│   │   └── EventRegistrationService.java
│   └── resources
│   └── application.properties
└── test
└── java
└── ca
└── mcgill
└── ecse321
└── eventregistration
└── service
├── event
│   └── TestCinema.java
├── payment
│   ├── TestPaymentWithCreditCard.java
│   ├── TestPaymentWithCreditCardData.java
│   └── TestUtils.java
└── role
├── PromoterRoleTestData.java
└── TestPromoterRole.java
Additionally, Here it my build.gradle file
buildscript {
ext {
springBootVersion = '2.1.2.RELEASE'
}
repositories {
mavenCentral()
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
}
}
apply plugin: 'java'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'
group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'
repositories {
mavenCentral()
}
dependencies {
implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
implementation 'org.springframework.boot:spring-boot-starter-web'
runtimeOnly 'org.postgresql:postgresql'
testImplementation 'org.springframework.boot:spring-boot-starter-test'
}
This fixes my java problem, but I still cannot get it running as a spring boot application.
Please help as I am not sure where to continue!!! I need to be able to run this project as a spring boot application for backend services, as I will then be tasked with connecting it to frontend services with vue.js. (Don't worry i got that part)!
Here is my EventRegistration.java file as well
package ca.mcgill.ecse321.eventregistration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.SpringApplication;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;
#RestController
#SpringBootApplication
public class EventRegistrationApplication {
public static void main(String[] args) {
SpringApplication.run(EventRegistrationApplication.class, args);
}
#RequestMapping("/")
public String greeting() {
return "ECSE321 Event Registration Application - Backend base URL.\n"
+ "Use the API methods to interact with the backend!";
}
}

Though I stopped using eclipse but following used to solve situations like this
1.
- Eclipse ->preferences-->java-->installed JRE --> select a standard vm
(can find here jdk1.8.0_51.jdk/Contents/Home)
2.
- add the JRE System Library to your project build path
- right click project > select build path > libraries >
- if JRE is listed then good otherwise > add Library
- select JRE library and finish

Javalite framework - problem with locating existing FreeMarker templates

I am developing a simple web application which provides RestFul API for managing several resources.
I am using java standard edition - openjdk version "1.8.0_191 and the following javalite dependencies:
javalite-common-2.3-SNAPSHOT.jar
activejdbc-2.3-SNAPSHOT.jar
activeweb-2.3-SNAPSHOT.jar
activeweb-testing-2.3-SNAPSHOT.jar
freemarker-2.3.28.jar
I use embedded jetty v9.4.1 for web server and the whole project is packed as jar with dependencies and is run using the following command:
java -Dconfig=/etc/project/config.properties -jar jarname.jar
The web application is designed to serve only JSON and all FreeMarker templates construct json messages. Here is my FreeMarker config class:
public class FreeMarkerConfig extends AbstractFreeMarkerConfig {
#Override
public void init() {
// this is to override a strange FreeMarker default processing of numbers
Configuration config = this.getConfiguration();
config.setNumberFormat("0.##");
config.setClassicCompatible(true);
config.setClassForTemplateLoading(this.getClass(), "webapp/WEB-INF/views");
}
}
After the packaging the structure inside the jar is as follows (this is a simplified version with only one resource):
├── META-INF
│   ├── MANIFEST.MF
│   └── maven
│   └── project.control
│   └── panel
│   ├── pom.properties
│   └── pom.xml
├── activejdbc_models.properties
├── app
│   ├── config
│   │   ├── AppBootstrap.class
│   │   ├── AppControllerConfig.class
│   │   ├── DbConfig.class
│   │   ├── FreeMarkerConfig.class
│   │   └── RouteConfig.class
│   ├── controllers
│   │   ├── APIController.class
│   │   ├── CatchAllFilter.class
│   │   ├── OfficesController.class
│   └── models
│   ├── Office.class
├── config.properties
├── project
│   └── control
│   └── panel
│   ├── Launcher.class
│   ├── dao
│   │   ├── query
│   │   │   ├── Query.class
│   │   │   ├── QueryBuilder.class
│   │   │   ├── QueryStringBuilder.class
│   │   │   ├── StatsParamsHandler.class
│   │   └── validators
│   │   ├── OfficeValidator.class
│   ├── exceptions
│   │   └── ResourceNotFoundException.class
│   └── util
│   ├── Config.class
│   ├── JsonHelper.class
└── webapp
└── WEB-INF
├── views
│   ├── offices
│   │   ├── _comma.ftl
│   │   ├── _office.ftl
│   │   ├── _office_agency.ftl
│   │   ├── _office_agent.ftl
│   │   └── index.ftl
│   ├── layouts
│   │   └── default_layout.ftl
│   ├── shared
│   │   ├── _paging.ftl
│   │   └── message.ftl
│   ├── system
│   │   ├── 404.ftl
│   │   └── error.ftl
└── web.xml
Most of the time everything seems to operate normally and without any problems. But at some point something happens and FreeMarker is unable to locate the templates which were previously served multiple times.
I am not able to reproduce the behaviour on localhost so I am not able to debug it.
It happened several times while running on a server. The only observation I had is that it happens after several idle hours - i.e there were no requests for several hours, the next request fails because FreeMarker can't locate the needed template. Here is the exact exception which is thrown, when /offices is requested:
2019-06-24 15:22:50 - INFO LazyList:164 - {"sql":"SELECT * FROM offices ORDER BY id LIMIT 20 OFFSET 0 ","params":[],"duration_millis":2,"cache":"miss"}
2019-06-24 15:22:50 - INFO DB:164 - {"sql":"SELECT COUNT(*) FROM offices","params":[],"duration_millis":0}
2019-06-24 15:22:50 - INFO FreeMarkerTemplateManager:81 - Rendering template: '/offices/index.ftl' without layout.
2019-06-24 15:22:50 - INFO FreeMarkerTemplateManager:81 - Rendering template: '/shared/message.ftl' without layout.
2019-06-24 15:22:50 - INFO RequestDispatcher:360 - {"controller":"app.controllers.OfficesController","duration_millis":15,"remote_ip":"127.0.0.1","method":"GET","action":"index","error":"Failed to render template: '/shared/message.ftl' without layout. Template not found for name \\\"/shared/message.ftl\\\".\\nThe name was interpreted by this TemplateLoader: WebappTemplateLoader(subdirPath=\\\"/WEB-INF/views/\\\", servletContext={contextPath=\\\"\\\", displayName=\\\"activeweb\\\"}).","url":"http://127.0.0.1:5050/offices","status":404}
2019-06-24 15:22:50 - INFO FreeMarkerTemplateManager:81 - Rendering template: '/system/404.ftl' with layout: '/layouts/default_layout.ftl'.
2019-06-24 15:22:50 - ERROR RequestDispatcher:290 - ActiveWeb internal error:
org.javalite.activeweb.ViewMissingException: Failed to render template: '/system/404.ftl' with layout: '/layouts/default_layout.ftl'. Template not found for name "/system/404.ftl".
The name was interpreted by this TemplateLoader: WebappTemplateLoader(subdirPath="/WEB-INF/views/", servletContext={contextPath="", displayName="activeweb"}).
at org.javalite.activeweb.freemarker.FreeMarkerTemplateManager.merge(FreeMarkerTemplateManager.java:109)
at org.javalite.activeweb.RenderTemplateResponse.doProcess(RenderTemplateResponse.java:88)
at org.javalite.activeweb.ControllerResponse.process(ControllerResponse.java:67)
at org.javalite.activeweb.RequestDispatcher.renderSystemError(RequestDispatcher.java:283)
at org.javalite.activeweb.RequestDispatcher.doFilter(RequestDispatcher.java:219)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1613)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:541)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:190)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1584)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:188)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1228)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:168)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:481)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1553)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:166)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1130)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.Server.handle(Server.java:564)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:320)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:251)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:279)
at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:112)
at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:124)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:672)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:590)
at java.lang.Thread.run(Thread.java:748)
Additional details can be provided in case of need.
What may cause such problems - while everything seems operational, suddenly FreeMaker can't locate templates which were previously served without any problems.
Any suggestions that may help for debugging the issue will be appreciated.
Thanks!

After more detailed investigation it appeared that jetty extracts the FreeMarker templates from the jar and places them in /tmp folder. The folder has the following pattern
/tmp/jetty-<host>-<port>-<resourceBase>-<context>-<virtualhost>-<randomdigits>.dir
Example:
jetty-0.0.0.0-5050-webapp-_-any-35239075401795634.dir
Unix based operation systems have policy for cleaning /tmp folder and after the folder is deleted - obviously the templates can't be found.
The solutions is to configure jetty's WebAppContext to use another directory for this kind of data. This can be done with setTempDirectory method:
String webViewsPath = Launcher.class.getResource("/webapp").toString();
WebAppContext webapp = new WebAppContext(webViewsPath, "/");
webapp.setTempDirectory(new File("/data/templates"));
server.setHandler(webapp);
More information for jetty's temporary directories can be found here:
https://www.eclipse.org/jetty/documentation/9.4.x/ref-temporary-directories.html

Java Spring MVC - Uploading and storing file inside "webapp" folder is bad idea? Why is it?

When it comes to uploading a file in Spring MVC, I found many articles suggesting that you should store it into the file-system folder rather than folder inside of a project.
But My web-app render HTML(view)page using a file from a folder inside webapp folder.
├── src
│   ├── main
│   │   ├── java
│   │   │   └── com // Where my application's is.
│   │   ├── resources
│   │   │   ├── META-INF
│   │   │   ├── log4j.xml
│   │   │   ├── maildata.properties
│   │   │   └── persistence-mysql.properties
│   │   └── webapp
│   │   ├── WEB-INF
│   │   │   ├── classes
│   │   │   ├── spring
│   │   │   ├── templates // Where my view pages are. Thymeleaf template used.
│   │   │   │   ├── login.html
│   │   │   │   ├── index.html
│   │   │   │   └── ...html and More...
│   │   │   └── web.xml
│   │   └── resources // --> This is location that my app use for rendering.
│   │   ├── css
│   │   ├── fonts
│   │   ├── images
│   │   ├── js
│   │   └── vendors
│   └── test
│   ├── java
│   │   └── com
│   └── resources
│   └── log4j.xml
└── target
in my View part, I use files from resources folder to render the HTML page.
.
.
<link rel="stylesheet" th:href="#{'/resources/css/style.css'}" type="text/css">
.
.
.outbox {
background:
url([[#{/resources/images/header.jpg}]]) #000
55% 0 no-repeat;
background-size: 140% auto;
margin-top: -68px;
width: 100%;
padding-top: 42.25%;
position: relative;
display: block;
z-index: -1;
}
.
.
.
I want to make functionality that uploading a file into the resources folder and using it for rendering HTML page.
Is this a bad idea? Could you explain why?
If so, what's the best approach I can take for my task? (The Best location that for uploading files)

If you undeploy the application, what will happen to all files uploaded to the resources folder? I believe they will be deleted along with the rest of the application. If that doesn't matter to you, then you are fine to upload to that direct. If instead you want the files to persist between deployments, you should either:
Upload them to a different directory on the file system. One that isn't managed by a server.
Upload them to a database table as a BLOB.
In either case, you will need to make a controller that returns the image as a file (because they are no longer accessible as resources).

Multi-module Spring project: override a resource file in test

I have a Spring project with the following structure:
.
├── pom.xml
├── core-module
│   ├── pom.xml
│   └── src
│   ├── main
│   │   ├── java
│   │   └── resources
│   │   ├── applicationContext.xml
│   │   └── file.xml
│   └── test
│   ├── java
│   └── resources
│   ├── file.xml
│   └── foo.xml
└── web-module
├── pom.xml
└── src
├── main
│   └── java
└── test
└── java
In my applicationContext.xml file, I have the following import:
<import resource="classpath:file.xml" />
In production I want to use the file.xml defined in main, and during tests I want to use the one defined in the test folder; it's actually what is happenning when I run the tests of the core-module.
However, when I run the tests of the web-module, this is not the case, the file used is the one of the main folder.
How to perform what I want?
Some notes:
web-module has a test-jar dependency to core-module, so tests resources are included;
if I go inside the target directory, the file.xml is the good one in the test-classes folder;
when running web-module tests, if I put a breakpoint in the Spring code, then a getClass().getClassLoader().getResource() on file.xml returns the one defined in main, but if I run the same method on the foo.xml file it returns me the only one available in the test folder, so both files seems to be present, but it acts as if the main takes over the test resource...
Thank you!

Package does not exist IntelliJ

I'm using IntelliJ to develop a java application but I'm not able to import any of the packages I created. I marked my src folder as Sources Root and the tree suggests I'm able to import a package by just
import service.RMI;
on my App.java file.
but when I try to compile
javac App.java
I get an error saying
App.java:4: error: package service does not exist
import service.RMI;
^
Does anyone knows why this happens? Does it have to do with my project skeleton?
For a better understanding, I leave my project tree:
.
├── algorithms
│   └── SHA256.java
├── app
│   ├── App.class
│   └── App.java
├── file
│   ├── ChunkFile.java
│   └── Chunk.java
├── filesystem
│   └── filesystem.java
├── META-INF
│   └── MANIFEST.MF
├── peer
│   ├── listeners
│   │   ├── MClistener.java
│   │   └── MDBlistener.java
│   └── Peer.java
├── protocols
│   ├── Backup.java
│   ├── Delete.java
│   └── Restore.java
└── service
└── RMI.java

I found the solution.
I was compiling all wrong. I was trying to run
javac App.java
on my app directory but I figured out that I need to run
javac app/App.java
on my root directory - src, and then, to run the app I need
java app.App
Thanks for the kind replies.
Regards